Book IV chapter 5

Superfoetation does not occur at all in some animals but does in others; of the former some are able to bring the later formed embryo¹ to birth, while others can only do so sometimes. The reason why it does not occur in some is that they produce only one young one, for it is not found in solid-hoofed animals and those larger than these, as owing to their size the secretion² of the female is all used up for the one embryo. For all these have large bodies, and when an animal is large its foetus is large in proportion, e.g. the foetus of the elephant is as big as a calf³. But superfoetation occurs in those which produce many young because the production of more than one at a birth is itself a sort of superfoetation, one being added to another. Of these all that are large, as man, bring to birth the later embryo, if the second impregnation takes place soon after the first, for such an event has been observed before now. The reason is that given above, for even in a single act of intercourse⁴ the semen discharged is more than enough for one embryo, and this being divided causes more than one child to be born, the one of which is later than the other. But when the embryo has already grown to some size and it so happens that copulation occurs again, superfoetation sometimes takes place, but rarely, since the uterus generally closes in women during the period of gestation⁵. If this ever happens (for this also has occurred) the mother cannot bring the second embryo to perfection, but it is cast out in a state like what are called abortions⁶. For just as, in those animals that bear only one, all the secretion of the female is converted to the first formed embryo because of its size, so it is here also; the only difference is that in the former case this happens at once, in the latter when the foetus has attained⁷ to some size, for then they are in the same state as those that bear only one. In like manner, since man naturally would produce many young, and since the size of the uterus and the quantity of the female secretion are both greater than is necessary for one embryo, only not so much so as to bring to birth a second, therefore women and mares are the only animals which admit the male during gestation, the former for the reason stated, and mares both because of the barrenness of their nature and because their uterus is of superfluous⁹ size, too large for one but too small to allow a second embryo to be brought to perfection by superfoetation. And the mare⁸ is naturally inclined to sexual intercourse because she is in the same case as the barren among women; these latter are barren because they have no monthly discharge (which corresponds to the act of intercourse in males) and mares have exceedingly little. And in all the vivipara the barren females are so inclined, because they resemble the males when the semen has collected in the testes but is not being got rid of. For the discharge of the catamenia is in females a sort of emission¹⁰ of semen, they being unconcocted semen as has been said before. Hence it is that those women also who are incontinent in regard to such intercourse cease from their passion for it when they have borne many children, for, the seminal¹¹ secretion being then drained off, they no longer desire this intercourse. And among birds the hens are less disposed that way than the cocks, because the uterus of the hen-bird is up near the hypozoma; but with the cock-birds it is the other way, for their testes are drawn¹² up within them, so that, if any kind of such birds has much semen naturally, it is always in need of this intercourse. In females then it encourages copulation to have the uterus low down, but in males to have the testes drawn up.

It has been now stated why superfoetation is not found in some animals at all, why it is found in others which sometimes bring the later embryos¹³ to birth and sometimes not, and why some such animals are inclined to sexual intercourse while others are not.

Some of those animals in which superfoetation occurs can bring the embryos to birth even if a long time elapses between the two impregnations, if their kind is spermatic, if their body is not of a large size, and if they bear many young. For because they bear many their uterus is spacious¹⁴, because they are spermatic the generative discharge is copious¹⁵, and because the body is not large but the discharge is excessive and in greater measure than is required for the nourishment¹⁶ wanted for the embryo, therefore they can not only form animals but also bring them to birth later on. Further, the uterus in such animals does not close up during gestation because there is a quantity of the residual¹⁷ discharge left over. This has happened before now even in women, for in some of them the discharge continues during all the time of pregnancy¹⁸. In women, however, this is contrary to Nature, so that the embryo suffers, but in such animals it is according to Nature, for their body is so formed from the beginning, as with hares. For superfoetation occurs in these animals, since they are not large and they bear many young (for they have many toes and the many-toed animals bear many), and they are spermatic. This is shown by their hairiness, for the quantity of their hair is excessive, these animals alone having hair under the feet and within the jaws¹⁹. Now hairiness is a sign of abundance of residual matter, wherefore among men also the hairy are given to sexual intercourse and have much semen rather than the smooth. In the hare it often happens that some of the embryos are imperfect while others of its young are produced perfect.

1 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

2 secretion   

n.分泌

参考例句：

• Is there much secretion from your eyes?你眼里的分泌物多吗？
• In addition,excessive secretion of oil,water scarcity are also major factors.除此之外，油脂分泌过盛、缺水也都是主要因素。

3 calf   

n.小牛，犊，幼仔，小牛皮

参考例句：

• The cow slinked its calf.那头母牛早产了一头小牛犊。
• The calf blared for its mother.牛犊哞哞地高声叫喊找妈妈。

4 intercourse   

n.性交；交流，交往，交际

参考例句：

• The magazine becomes a cultural medium of intercourse between the two peoples.该杂志成为两民族间文化交流的媒介。
• There was close intercourse between them.他们过往很密。

5 gestation   

n.怀孕；酝酿

参考例句：

• The gestation period can be anything between 95 and 150 days.妊娠期从95天至150天不等。
• This film was two years in gestation.这部电影酝酿了两年。

6 abortions   

n.小产( abortion的名词复数 )；小产胎儿；（计划）等中止或夭折；败育

参考例句：

• The Venerable Master: By not having abortions, by not killing living beings. 上人：不堕胎、不杀生。 来自互联网
• Conclusion Chromosome abnormality is one of the causes of spontaneous abortions. 结论：染色体异常是导致反复自然流产的原因之一。 来自互联网

7 attained   

（通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况）

参考例句：

• She has attained the degree of Master of Arts. 她已获得文学硕士学位。
• Lu Hsun attained a high position in the republic of letters. 鲁迅在文坛上获得崇高的地位。

8 mare   

n.母马，母驴

参考例句：

• The mare has just thrown a foal in the stable.那匹母马刚刚在马厩里产下了一只小马驹。
• The mare foundered under the heavy load and collapsed in the road.那母马因负载过重而倒在路上。

9 superfluous   

adj.过多的，过剩的，多余的

参考例句：

• She fined away superfluous matter in the design. 她删去了这图案中多余的东西。
• That request seemed superfluous when I wrote it.我这样写的时候觉得这个请求似乎是多此一举。

10 emission   

n.发出物，散发物；发出，散发

参考例句：

• Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。
• Finally,the way to effectively control particulate emission is pointed out.最后，指出有效降低颗粒排放的方向。

11 seminal   

adj.影响深远的；种子的

参考例句：

• The reforms have been a seminal event in the history of the NHS.这些改革已成为英国国民保健制度史上影响深远的一件大事。
• The emperor's importance as a seminal figure of history won't be diminished.做为一个开创性历史人物的重要性是不会减弱的。

12 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。

13 embryos   

n.晶胚；胚，胚胎( embryo的名词复数 )

参考例句：

• Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段，而且其行为象胚。 来自辞典例句
• Evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句

14 spacious   

adj.广阔的，宽敞的

参考例句：

• Our yard is spacious enough for a swimming pool.我们的院子很宽敞，足够建一座游泳池。
• The room is bright and spacious.这房间很豁亮。

15 copious   

adj.丰富的，大量的

参考例句：

• She supports her theory with copious evidences.她以大量的例证来充实自己的理论。
• Every star is a copious source of neutrinos.每颗恒星都是丰富的中微子源。

16 nourishment   

n.食物，营养品；营养情况

参考例句：

• Lack of proper nourishment reduces their power to resist disease.营养不良降低了他们抵抗疾病的能力。
• He ventured that plants draw part of their nourishment from the air.他大胆提出植物从空气中吸收部分养分的观点。

17 residual   

adj.复播复映追加时间；存留下来的，剩余的

参考例句：

• There are still a few residual problems with the computer program.电脑程序还有一些残留问题。
• The resulting residual chromatism is known as secondary spectrum.所得到的剩余色差叫做二次光谱。

18 pregnancy   

n.怀孕，怀孕期

参考例句：

• Early pregnancy is often accompanied by nausea.怀孕早期常有恶心的现象。
• Smoking during pregnancy increases the risk of miscarriage.怀孕期吸烟会增加流产的危险。

19 jaws   

n.口部；嘴

参考例句：

• The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
• The scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。